1. Technical Field
The present invention relates generally to an apparatus for calibrating an apparatus for retrieving objects from an array of storage cells.
2. Description of Related Art
Storage library systems are capable of storing and rapidly retrieving large quantities of information stored on storage media cartridges. Such storage library systems often use robotic mechanisms to improve the speed of information retrieval and the reliability of maintaining the storage library cartridge inventory. These robotic mechanisms typically comprise a hand mechanism positioned on a movable arm. To retrieve information, the robotic arm is moved to position the hand near the inventory location of a desired media cartridge. The hand is then activated to grip the desired cartridge and remove it from the library inventory location. The robotic arm with the hand gripping the cartridge then moves to an appropriate position to further process the cartridge. In this manner, the robotic hand manipulates the cartridge for access to information stored on the cartridge.
However, in order to grip the cartridge, the position of the robotic arm with respect to the cartridge within the library must be determined. Positional accuracy of the robotic arm and any devices attached thereto affects both the repeatability of an operation as well as the ability of the robotic arm to accurately perform the particular task required of it. There are many different arm calibration arrangements known in the art, and many of these entail the use of some sort of sensor to determine the position of the robotic arm.
A common method of calibrating the position of the robotic arm gripper mechanism is to use a vision system to orient the robotic arm with respect to one or more baseline targets located in the work space. Often these vision systems are located underneath or above the robotic arm and are oriented at an angle relative to the robotic arm. These vision systems are located at an angle so that a target on the work space can be imaged, and then a target located on a part of the robotic arm that is extended into the field of view of the vision system is imaged. The two images are compared and the position of the robotic arm is adjusted such that the target on the robotic arm is aligned with the target on the work piece when extended.
However, orienting the vision system at an angle causes the inclusion of the vision system with the robotic arm to take up a large amount of space. Thus, a significant portion of the space within the storage library system is unusable for placing storage cells. This is due to the fact that if, for example, the vision system is located below the robotic arm, an amount of space equal to the height or thickness of the angled vision system at the bottom of the storage retrieval system cannot be accessed by the robotic arm since the vision system comes into contact with the floor of the storage library system before the robotic arm. Thus the robotic arm is prevented from going low enough within the storage library system to engage and retrieve an object stored in a storage cell located within the thickness of the angled vision system from the floor of the storage library system.
However, as the need to store more and more data increases and the price paid for space also increases, the amount of money necessary to store data is increased. Thus, the wasted space within a library storage system becomes more and more intolerable. Therefore, there is a need for a calibration system that requires less space than current systems and that allows for a denser concentration of storage cells within a storage library system.
The present invention provides a calibration apparatus for use with a storage system for storing a plurality of objects in an array of object storage locations. In a preferred embodiment, the calibration apparatus includes a target affixed in a predetermined location to the storage system, an object retrieval mechanism, and an imaging system. The object retrieval mechanism is used for retrieving objects from the object storage locations and has a principal direction of movement which is perpendicular to a plane in which an exposed surface of each of the plurality of objects lie. The imaging system is attached to the object retrieval mechanism for imaging the target. The imaging system is positioned such that the direction from the target to the imaging system is parallel to the principal direction. Thus, the thickness of the housing for the imaging system for the present invention is reduced over that needed to hold the imaging system in the prior art.
In another embodiment, the calibration apparatus includes an object retrieval mechanism, a calibration block, a first sensor, and a second sensor. The object retrieval mechanism is configured to retrieve objects from object storage locations within a library storage system. The calibration block is configured to receive a portion of the object retrieval mechanism. The first sensor on the calibration block determines the position of the object retrieval mechanism with respect to the calibration block in a first direction and the second sensor on the calibration block determines the position of the object retrieval of the object retrieval mechanism with respect to the calibration block in a second direction. The first and second directions are substantially orthogonal to each other.